1. Field of the Invention
This invention relates to a method and apparatus for fusion joining polyethylene pipe using a frequency converter and/or power supply mounted within a housing that can be easily moved to an installation site. Many different suitable power sources can be used to feed the power supply with an input power. The power source, such as a generator on a truck, conventional line power or a battery pack, can be located remote from the installation site.
2. Description of Prior Art
Many different methods and apparatuses exist for fusion joining polyethylene pipe, such as with electrofusion fittings or induction fusion fittings. In conventional electrofusion methods, a pipe coupling or other fitting normally has a wire coil molded within the coupling or other fitting. Electrical leads, contacts or electrodes are often mounted on an external portion of the coupling body, for electrical contact access. In a typical conventional electrofusion procedure for axially joining two pipes, each pipe end portion is cleaned, scraped and then positioned within a coupling receiver. A clamp is often used to secure or hold the pipe with respect to the coupling. Power is supplied directly to a wire coil molded within the coupling. The wire coil then transfers heat to the polyethylene material and fuses the coupling material directly to the pipe material.
In conventional induction fusion procedures, a rigid heater element is molded within the coupling or other fitting. The coupling provides no direct access to external contacts or electrodes electrically connected to the rigid heater element. Current flow through the rigid heater element is generated by induction from a primary coil within an application tool that is positioned around the coupling or other fitting. Normally, a high frequency current is delivered to the application tool for a predetermined time period. A primary coil within the application tool is energized and then induces a secondary current within the rigid heater element. The temperature of the rigid heater element increases to a generally constant value and then the polyethylene material or other plastic material surrounding the rigid heater element fusion bonds the polyethylene or other plastic material of the pipe and the coupling or other fitting.
In many conventional processes associated with either electrofusion or induction fusion heating, the power delivered to the wire coil of an electrofusion fitting or a heater element of an induction fusion fitting, necessitates relatively heavy gauge or large cables that must be relatively short, due to the high current and high frequency power waveform transmitted through the cables. Thus, it is often necessary to position the power source relatively close to an installation site or fusion site. Quite often significant amounts of labor and time are necessary to setup and breakdown power equipment necessary to deliver power requirements demanded by the installation tool.
There is an apparent need for a method and apparatus that can be more conveniently used at an installation site or a fusion site.